Varicella-zoster virus (VZV) is the etiologic agent of chickenpox and herpes zoster. We have developed a system to generate recombinant VZV by transfecting tissue culture cells with four overlapping VZV cosmid DNAs. Mutations have been engineered into the cosmids that result in VZV that is unable to express the viral thymidylate synthetase, glycoprotein V, or ribonucleotide reductase genes. Viruses that are unable to express the former two genes grow at similar rates as the parental virus, while virus that is unable to express the ribonucleotide reductase gene grows at a slower rate than wild-type virus. Selected VZV mutants will used to inoculate guinea pigs to determine if the viruses have lost the ability to establish latency in the central nervous system. Foreign genes have been inserted into the VZV genome. The E. coli beta- galactosidase gene, has been inserted into the VZV genome, and the resultant virus produces plaques that stain blue with X gal. This virus has been inoculated into guinea pigs to determine the types of cells that are able to support viral replication and establishment of latency. The herpes simplex virus (HSV) glycoprotein D (gD) gene, encoding a major neutralizing antigen, has been inserted into VZV and the resulting virus expresses high levels of HSV gD on the surface of infected cells. Animals will be inoculated with VSV expressing HSV gD to determine if they are protected against infection with HSV. A cell line has been developed that secretes VZV glycoprotein II (gpII), an important neutralizing antigen. Guinea pigs will be injected with recombinant VZV gpII and challenged with live VZV to determine if they are protected from infection with VZV.